Computing devices, such as mobile phones, cell phones and smart phones, are becoming more ubiquitous and versatile. As demand grows, computing device design also grows to support more security features, such as a device lock. When a user is not using the computing device, the user may lock the computing device to prevent others from having full access to all its features and information. Computing devices use many different methods to authenticate a user to allow access to the device and its contents. Some of these methods including entering a text or numerical password, fingerprint entry using a biometric sensor, or touching a pattern on a touch screen display. When the user wishes to use the computing device, the user may unlock the phone by entering an authentication code using one of these methods.
However, it may not always be safe for the user to unlock the phone in this manner. For example, other people may be looking at the user to steal the code as the user enters it. Furthermore, the user may leave prints or smudges on a display screen that another person could use to steal the code.